1. Field of the Invention
The present invention relates generally to antennas, and more specifically to small antenna structures possessing diversity characteristics.
2. Discussion of the Related Art
A multipath environment is created when radio frequency (RF) signals propagate over more than one path from the transmitter to the receiver. Alternate paths with different propagation times are created when the RF signal reflects from objects that are displaced from the direct path. The direct and alternate path signals sum at the receiver antenna to cause constructive and destructive interference, which have peaks and nulls. When the receiver antenna is positioned in a null, received signal strength drops and the communication channel is degraded or lost. The reflected signals may experience a change in polarization relative to the direct path signal. This multipath environment is typical of indoor and in-office wireless local area networks (WLAN).
An approach to addressing the multipath problem is to employ multiple receiver antenna elements in order to selectively receive a signal from more than one direction or from a slightly different position. This approach, known as xe2x80x9cdiversityxe2x80x9d, is achieved when receiving signals at different points in space or receiving signals with different polarization. Performance is further enhanced by isolating the separate antennas. Wireless communication link bit error rate (BER) performance is improved in a multipath environment if receive and/or transmit diversity is used.
Conventional antenna structures that employ diversity techniques tend to be expensive and physically large structures that utilize bulky connectors, such as coaxial cable connectors. Such antenna structures are not suitable for residential and office use where low-cost and small physical size are highly desirable characteristics. Furthermore, such antenna structures cannot be easily mounted or attached to the numerous different types of devices that may need to communicate in a WLAN. Thus, there is a need for antenna structures capable of employing diversity techniques that overcomes these and other disadvantages.
The present invention advantageously addresses the needs above as well as other needs by providing an antenna assembly that includes a portion of a first wall of a housing and a portion of a second wall of the housing. The first and second walls are noncoplanar. At least two antenna elements are included with a first of the at least two antenna elements being attached to the portion of the first wall and a second of the at least two antenna elements being attached to the portion of the second wall. Active circuitry is attached to a backside of at least one of the portion of the first wall and the portion of the second wall. The active circuitry is coupled to the at least two antenna elements.
In another embodiment, the invention can be characterized as an antenna assembly that includes a base having first and second plates that are noncoplanar and that are joined together. At least two antenna elements are included with a first of the at least two antenna elements being attached to the first plate and a second of the at least two antenna elements being attached to the second plate. Active circuitry is attached to a backside of at least one of the first and second plates. The active circuitry is coupled to the at least two antenna elements.
In a further embodiment, the invention can be characterized as a method that includes a method of making an antenna assembly. The method of making an antenna assembly includes the steps of: forming a base having first and second plates that are noncoplanar and that comprises a shape that conforms to a portion of a housing; attaching at least two antenna elements to the base with a first of the at least two antenna elements being located on a front side of the first plate and a second of the at least two antenna elements being located on a front side of the second plate; attaching active circuitry to a back side of at least one of the first and second plates; and coupling the active circuitry to the at least two antenna elements.